So close to running, but then this happened!

If you could get a small torch tip to it and heat all that material to cherry red, that would anneal it so it could be drilled. With a little effort the engine could be rotated a few degrees to improve access.
In any case , If the header is there I would remove it and place a cast iron manifold there to serve as pilot for my drill. I would recommend a carbide drill even though the steel was annealed. Masonry bits have carbide insert tips.